The exemplary embodiment relates to the management of print jobs in a manner which enables a reduction in overall energy consumption. It finds particular application in conjunction with a network printing system in which multiple shared printers are available for printing print jobs and will be described with particular reference thereto.
Network printing systems, in which print jobs can be selectively directed from a workstation to one of a group of shared devices, are now common. The network devices are typically printers or multifunction devices (MFDs), such as those with printing, copying and optionally faxing and email capability, all of which will be referred to as printers. A device typically receives an incoming print job and places it in a queue with other print jobs and then prints them in order. Since demands for printing vary over time, the devices typically have two or more modes in which the printer is either capable of printing or capable of being automatically raised to a mode in which it is capable of printing. A printer may thus have at least two modes including a ready mode, in which the device is ready for printing, and a stand-by or automatic power saving mode. Generally, when the printer has been idle for a certain period of time, it automatically goes into the stand-by mode, with reduced power consumption.
For certain printers, the difference in power consumption between stand-by and ready modes is significant. For example, in the case of printers using solid ink technology, the ink is melted to convert it from a solid to a liquid prior to printing. In the ready mode, the ink is maintained at an increased temperature level, resulting in higher power consumption. The warm-up from stand-by to ready mode involves significant energy consumption to melt the solid ink and also consumes ink to clean the print heads. Once the warm-up has been completed, the printer is ready for operation and starts printing (generally, after a quick transition through an idle state). When printing ends, the printer enters the idle state, where in the case of solid ink printers, the ink is maintained in liquid form. If no new print job is submitted to the printer, it will eventually return to its stand-by mode. In periods of infrequent usage, printers may go through numerous cycles like these, possibly one for every print job.
The wake-up process can be quite lengthy. Some printer models provide different levels of “readiness” to maintain an acceptable balance between power consumption and wake-up time, and in some cases they provide self-adaptive power-mode management by measuring the daily periods when printers are typically being used, in order to anticipate the wake-up and the transition to ready mode.
Typically, the handling of office print jobs aims to execute jobs immediately: jobs are added to the printer's print queue and sent to the printer if the printer is in a ready mode or warming-up state. If the printer is in the stand-by mode, a command is sent to wake it up. In a situation where the printer is infrequently used, this may result in many daily wake-ups and periods when the printer is idle in the ready mode (i.e., the time following the execution of a print job when the printer remains in ready mode, “hoping” to receive new jobs). This form of “eager” printing has the advantage that latency for users is minimal: a requested print job is executed as soon as possible. In many cases, this may be the optimal behavior, but there are also many situations where users may be willing to accept a later printing, if this could lead to reduced consumption of power and/or consumables (e.g., ink, paper), and hence cost. For example, printing frequently occurs to prepare off-line reading, off-site working, meeting materials, and the like.
As organizations move to electronic, largely paperless systems, print jobs are more likely to be generated on an individual user basis, rather than centralized printing in bulk, as was the case in the traditional print-and-distribute model. The resulting distributed printing of a large number of smaller print jobs typically increases the number of times in a day that a printer switches operational modes.
There remains a need for print job management systems which are able to manage the power states of printers more efficiently.